Earlier quoted context omitted.
> Mainly: editing and saving directly in the debugger! Hum... Firefox does that. I know because every time I mistakenly start saving I ask what is the point of it. But well, looks like it's useful for somebody.
Erm, it can edit and save code live in a debbing session? Also, how can I edit code? It is non editable for me.
I believe you can activate it on the main build too, but I don't know how. Anyway, if you are debugging code, I highly recommend the developer version.
1 - That is a different configuration of the same code as the main build, for web developers. It's not for developing Firefox itself.